Sleep deprivation is common and increasing in prevalence in the American population. Loss of sleep has a number of adverse consequences. These include behavioral changes, impairment of cognition with an increased risk of motor vehicle crashes, and errors in the workplace. Moreover, sleep loss leads to metabolic changes with insulin resistance, increased appetite and is a risk factor for development of obesity. There are, however, substantial individual differences in the degree of impairment produced by sleep loss. This is heritable, i.e., a large part of the difference between individuals is genetic in oriin. Elucidating the genetic basis of the response to sleep loss will enable a more rationale scheduling in operations that require 24/7 activity, and will likely identify novel pathways that could be the basis of future pharmacological approaches to alter the consequences of sleep loss. Further study to elucidate genes involved in humans is, however, challenging since examination of the response to sleep deprivation requires expensive studies with a high protocol burden (four days in a laboratory). In this application an alternative approach to identify responsible genes is proposed, based on studies in mice. Response to sleep deprivation in mice varies between inbred strains but the gene variants responsible for this difference are unknown. This proposal plans to take advantage of the recently created diverse outbred strain of mice which are all genetically different. This strategy requires study of a large number of mice (in this application, 800) in a high throughput fashion. Hence, response to sleep deprivation will be assessed by a novel high throughput strategy based on digital video analysis. Video analysis not only provides accurate estimates of sleep and wake, but also of the stages of sleep-rapid-eye movement (REM) sleep and non-rapid-eye movement (NREM) sleep. All mice will not only be phenotyped but will be genotyped based on a new genotyping chip with 7,000 single nucleotide polymorphisms. This approach allows identification of a small region of the mouse genome associated with this quantitative trait. In addition, the normal duration of wakefulness that a mouse can sustain will also be simultaneously assessed. This, too, is a heritable trait that is highly relevant to the common problem of sleeping difficulty. Validation studies in relevant mice from the collaborative cross lines will be employed for both quantitative traits. Future studies will also extend this investigation into human populations using samples of well characterized individuals who have been studied with sleep loss and whose DNA is already available.